Sealed joint



Nov. 24, 1925.

E. T WEINTRAUB SEALED JOINT Filed Feb. 15, 192;:

2 SheetS- Shet ,1

INVENTOR ATTORNEYS Patented No 24, 1925.

UNITED STATES PATENT ounce.)

- nznenmn WEINTRAUB, or NE ILLY-sumsEINE, FRANCE.

SEALED JOINT.

Application filed February 15. 1923. Serial No. 619,173.

To all whom it may concern:

Be it known that I, EZECHIEL WEINTRAUB,

a citizen of the United States, residing athave lnvented cermetallic members extending from the exterior to the interior of an evacuated vessel. The pr1mary object ofthe invention is the provision of a, joint ofthe character referred to which is perfectly air-tight and which at the same time isa good electrical insulator.

Another ob'ect is to provide a joint hav.- ing the desire 'le properties previously mentioned and which is capable of rapidly conducting and dissipating heat, thereby insuring to a large extent against ruptures in or near the joint whichmight otherwise occur, due to excessive heat.

Still another object is the provision of a joint of this character, which is adapted to function as a high "voltage insulator, char-' acterized in that it is possessed of aghigh degree of mechanical strength.

Among the known methods for making joints for thepurposes herein referred to, those most generally used today involve a. simple mechanical clamping together of the parts to be joined with the interposition of a more or less plastic gasket such as asbestos, leather, etc., to which issometimes added a mercury seal. Joints of this kind are delicate, their mounting and dismo'untingis complicated, and erfect tightness is insuredonly with di culty.

.The present invention provides a joint cons'truetion (as well as a method for producing the same) which is absolutely perfect from the point of view of tightness, is readily mounted and taken apart, and admits of any degree of insulation desired. r

-The principal feature of the method involved in this inventionconsists, in that be tween the metallic parts to be joined there is limited to the, electrical arts.

interposed a layer of suitable substance such as glass, quartz, vltrie enamels, etc., whlch assume before fusion asoftened condition in which they readily adhere to the metaland whose respective coefficients of expansion are close to those of the metallic .parts to be joined together. The parts joined by this method form aperfect assemblage, being practically, 'if not literally, all of one piece. If the metallic parts between which a joint is to be made have quite similar coeflicients of expansion, a single interposed element or layer made of a material which coeflicient of expansion is about the same may be su'flicient, but if, on the other hand,

the parts to be joined have unequal coefIieients of expansion, or if the joint must have certain properties '(for instance, in high voltage insulators) which require the intercalation therein of elements suitable for the purpose having still another coefficient of expansion, the joint may include a pile-up of interposed elements usually in the form of plates, whose coefficients of expansion vary progressively (by amounts small enough to avoid danger of disruption or dislocation) between that-of the'metalsto be joined together and that of the special interpoiled element or elements.

According to another aspect of the invention, a joint is provided having the char acteristics of high insulation and mechanical 1 strength, as well as being a perfect vacuum seal. A joint of this type is particularly adj vantageous for use in vacuum apparatus intended for operation on .high tensions.

. The utility of the present invention is not The joints herein described, modified, perhaps, to. suit the particular problem in hand, are well adapted for use in vacuum bottles and for use-in conjunction wi'thwacuum, pumps. In fact, it is thought many other uses for such joints will occur as occasions arise;

7 As Specific. examples, t'wo steel plates may be joined according to the present method enamels, placing the enameled surfaces in contact, heating the parts in afurnace to a' temperature between 400 and 600 C. and sub ecting them to a pressure suflicient to cause them to. coalesce.

by enameling each with one of the usual steel The pressure may go up to afew kilograms per square centimetre. The temperature and pressure will vary with the nature of the enamel used, but shouldalways be selectedso as to cause perfect coalescence of the two enamel la ers, without causing excessive excretion 0 the enamel from between the two surfaces.

- the surfaces to be joined are covered with a layer of refractory glass such as Pyrex, which] has a coeflicient of expansion close to that of tungsten. The parts may be joined in the manner described above, but the temperature applied is of course higher than in the case of the softer enamels, being from 600 to 800C.

Instead of heating the parts in a furnace they can be heated by induction with high frequency currents.

In cases where the two metallic surfaces must be insulated from. each other in a vacuum-tight 'manner for higher voltages, the insulation provided for by the coalescing of the two enamel layers may not be suf-.

ficient, as the thickness of a good enamel that can be produced on steel is not much in excess of 1 mm. or 1% mm. If a glass or enamel plate of a nature similar to that of. u

' ments WlllCh are particularly characterized the enamel on the plates is interposed between the enameled plates and subjected to pressure and temperature as above, it is pos-,

sible to increase the thickness of. the enamel layer b a few millimetres, without causing undue ragility.

A better construction than that just described from the standpoint of combined high insulation and mechani'cal strength, may be obtained by an arrangement com prising a plurality of su erposed plates or rings with thin interposed layers of appropriate enamel. The number of such plates or rings employed in any particularcase depends upon the voltage whichit is desired to withstand. The total e ctive insulation of a joint of this kind is e ivalent to the sum of the effective insulat'on of the several layers of enamel. In a structure such as just other vitric substance is of considerable thickness and correspondingly more fragile,-

particularly with respect to compression stresses.

A further advantage. inherent in a joint such as that-last described arises from its relatively High thermic conductivity along a plane parallel to the sui face of the plates or ringsthe metal being a good heat conductor. This factor is'particularly impor abeaaes tant where the joint is employed in appadiameter or other expedients resorted to for avoiding having the edges of the adjacent plates coincide. Another expedient which ma be resorted to for avoiding surface lea age is to cover the exterior or interior surfaces of the assembled joint with a suitable insulating material in addition to the enamel. For a more detailed description of various embodiments of the invention, reference will now be made to the accompanying drawing, in which Fig. 1 is a fragmentary sectional view of a device including an evacuated vess'el'in which an electrode is inserted;

Fig. 2 illustrates a slight modification of that embodiment of the invention shown in Fig. 1;

Fig. 3 is an alternative form of joint, wherein the insulating properties are considerably enhanced;

Figs. 4:, 5, 6 and 7 are further alternative embodiments, each having its own particular utility; and

Figs. 8, 9, 10 and 11 show four embodimounted between the vessel A and the collar 1 G. In efi'ec'ting joinder of {parts here shown they are all heated to a temperature sufficient to soften the glass and mechanical pressure is exerted upon the collar C, thereby bringing about perfect adherence, on the one hand, between itself and the cylinder D, and on the other, between the cylinder D and the vessel A. -During the operation it is referable to surround the cylinder by a reractory mold (or a metallic mold lined with a refractory material such as graphite, etc.) I

in order to avoid cylinder.

Prior to this welding operation the collar C and the vessel A may be enameled on the surfaces which'are to come into contactwith the glass c 'linder. This-modification is indicated in ig. 2, wherein E refers to the enamel layer which is first applied to the metal surfaces. The layer of enamel E must of course be chosen so that its coefiicideformation 0 the glass ent of expansion is near that of steel or "medium of the layers of enamel by simple pressure at the softening temperature of the latter, provided the joint sufiiciently answers the requirements in additionto that,

of vacuum tightness, which might be imposed. This would be the case where only a moderately efficacious electrical insulator is required. The resulting joint is of extremely simple and strong construction and its tightness is perfect.

If a certain electrical insulation is to be obtained, the height of the cylinder 1). may be .made suflicient to enable the latter to resist the voltage applied, but it should be noted that the glasses, whose coefficients of expansion are about equal to that ,of steel, are only slightly refractory, and the insulating qualities are not of the best. In addition to this, owing to their chemical composition, they give rise to cathodic.

strains, which may be detrimental in electrio apparatus where cathodic emission comes into play.

The last-mentioned difi'iculty may be readily eliminated by the use of a tube F made of high class insulating material such. as porcelain, fused silica, etc. surrounding the electrode. The .tube F is in immediate con-' tact with the surface of the glass cylinder,

vessel.

The insulating properties of the joint maybe considerably improved by means of'the on the other han glass di s H are inserted,"- th e successive coetlicien of. expansion of which vary gradually f om that of porcelain to that of steel (assuming both the electrode andthe vessel-to be made of steel) The number of discs is such that the difi'er ence in' expansion between two welded ele ments remainsIt-o o smallto give rise to any dislocation of the structure whatever.

Any insulating substance other than por celain may of course be used for the cylinh der G, for instance, fused silica or a refractory" glass such as the one known under the trade name Pyrex. made between the various insulating substances will depend upon the particular voltage applied, upon the number of'pieces. to be joined together, and also upon the more or less high degree'of complexity to of expansion.

which is directed toward the interior of the proximately equal to The selection to be which any solution ofthe joint roblcm, would lead. With fused silica as t e insulator'G and the parts to be joined made of steel, it will be necessary to provide several discs of glass .between'the fused silica and each of the metal parts respectively. .A por- 'celain with .a coefficient of expansion sufli-- ciently high is available whereby only one glass disc is required for affecting the weld. If the parts to be joined are made of tungsten or molybdenum, certain ferro-nickel alloys or of any other substance having a coeflicient of expansion of the same order of magnitude are dealt with, they may be welded directly to a single lump of a refractory glass such as Pyrex, having high insulating qualities. Assembling the elements is accomplished as in the previous instances by exerting pressure, at the softening temperature of the glass, the joints of the interposed elements being made one after the other, starting with those which require the highest temperature.

The arrangement shown in Fig. 3 is particularly adapted for those cases where the partsto be welded have unequal coefficients The piled-up glass discs have such coeflicients of expansion as to vary pro- 'gressively between the coeflicients of expansion of the metallic parts to be joined.

In the structure of Fig. 4., the collar I is welded to the electrode B (which latter may. be made of any metal desired) and is made of a metal or alloy having a coefficient of expansion approximately the same as that of a high insulating refractory glass. A plate J made of the same metal or'alloy as the collar I is welded to the metallic vessel A, The cylinder K is made of a highinsulating refractory glass or equivalent substance, having approximately the .same coeflicient ofexpansion as-the collar I and'plate J.

Tungsten .or molybdenum are suitable met I als for the collar I and plate J, with which maybe used for the cylinder K a refractory glass having a coefficient of expansion ap- (3 to 4) 10', as for instance, Pyrex glass. Ferro-nickel alloys having appropriate composition may also be used for ferro-nickel alloys ranging from 30 to 44% nickel there may be obtained a whole series of coefficients of expansion ranging from zero to 5 x 10*, which series includes the coeflicients of expansion of the refractory and high insulating glasses up to fused silica.

.In the example of Fig. 5, the electrode B,

which may be made-of steel, is-welded to rods L, made of tungsten or molybdenum,

the parts I and J. With the latter being sealed into a mass of high insulatin g refractory glass M, the latter being welded according to the method-hereinbefore described. to' a plate of tungsten or molybdenum N, which latter lis in turn welded to the metallic vessel'A. This ar- 9 rangement is of particularadvantage in' those cases where the electrode does not have to conduct high amperage currents and hence where efficient cooling thereof need not be considered.

In Fig. 6 is shown a modification of the arrangement shown in Fig. 4, the plate J- being replaced by a cylinder 0.

In Fig. 7 the plate I of Fig. 4 is replaced by a cylinder P welded or secured in' any other manner to the steel electrode B through the medium ofa metal hood Q, which may be used as a cooling device.

In Figs. 8, 9, 10 and 11 are shown four ber bein sufficiently great so that the sum of the thickness of the successive enamel I layers provides sufficient insulating capacity for the voltage applied. Each of the enamel layers is sufficiently thin so'that the mass formed by the piled-up plates is not fragile.

Fig. 8 .illustrates a joint per so, without any associate apparatus. The 'metallic plates entering into the make-up of the joint are naturally given a shape appropriate to the purpose. In the examples chosen they are supposed to be built up from steel rings C (shown in cross sectionin the figures) which are welded together by lay ers of enamel D, having a thickness of .5 to 1.0 mm. As a rule a gentle pressure will be sufiicient to effectthe jointing operation,

at the softening temperature of the enamel. The weight of the piled-up metallic plates may moreover suffice to give the necessary pressure while the latter must at all times be smaller than that pressure at which part ofthe enamel would be squeezed out from between the metallic plates, thereby reducing by an undue amount the thickness of the layers of enamel after the welding operation.

Instead of the enameled iron or steel,

plates C, pieces made of other metals or alloys covered with enamels or appropriate glass may be used, for instance, copper ferro-nickel plates coated with crystal glass or other similar glasses, or tungsten plates.

coated with refractory glasses having a small coeflicient of expansion, such 'as the one known under the trade name Pyrex, etc. Frequently it might be advantageous to use metals or alloys in conjunction with enamels or high refractory glasses having small coefficients of expansion but being me- 'insulators; the resu ting built-up structures are better able to resist temperature changes or unequal temperature distribution.

The welding of the plates may be carried out to advantage in the electric furnace, the insulation of the built-up structure being controlled during the operation by any suitable means. In the embodiment shown in Fig. 9, the mass constituting the joint structure made in accordance with Fig. 8 is mounted between the wall A and a metallic collar E, carried by the rod B. The metallic plates at the ends of the built-up mass are welded by autogenous welding or are brazed, or secured b any other equivalent means to the collar and the wall A. An insulating sleeve F slidably mounted on the rod B provides the-insulation between this rod and the edges of the hole left in the wall A and also the inner edges of the metallic plates 0 forming part of the built-up joint.

It may be desirablein some instances to make the metallic plates of the built-up joint structure of various diameters so as toincrease the distance over which any surface discharge is compelledto travel, thereby avoiding such discharges. Fig. 10 shows an arrangement of this character wherein it will be seen that the alternate plates C are of different diameter. be accomplished in some cases by merely coating the outer surface of the structure with an insulating enamel, without providing plates of different ldiam'eters.

In the arrangement of the joint there must be taken into consideration the conditions arising from the welding of the ex-- treme metallic plates of the joint to the parts A and B, which are required to be joined together in order to avoid the danger of formation of cracks in the joint as the result .of the heat liberated in this welding operation. An arrangement such as the one shown in Fig. 11 may be adopted, in which the outermost parts G and H of the builtup structure aregiven such a shape and dimension that the points I and J where they are to be welded to the vessel A and electrode B respectively, are sufficiently remote from the enamel or glass layers D.

A Joints constructed in accordance with the embodiments of the invention shown in Figs; 8, 9, 10 and 11 are not only of value Where high insulation is required, but they are also useful in numerous instances where a good thermo insulator is desired, as for instance, the joints between the outer and inner jackets of metallic thermos bottles, diffusion pumps, etc. For these latter pur-' poses the thermo insulation afforded by the enamel or glass layers of the present joint meets all the requirements.

The same object-may The particular embodiments of the invention shown in thedrawings are given only by way of example and are not to be construed as limiting the invention in any respect.

I claim:

1. An electrical device comprising an evacuated vessel, an electrode extending from the exterior to the interior of said vessel, and an airtight joint interposed between said electrode and said Vessel, said joint comprising a pair of metallic members having substantially parallel adjacent surfaces, and a layer of fusible nonconducting vitric material having a coeflicient of expansion substantially equal to that of the metallic members, said layer being interposed between and adhering to "said surfaces. a]

2. An electrical device comprising an evacuated vessel, an electrode element within said vessel, said electrode element terminating at the exterior of said vessel and an airtight, non-conducting joint between said electrode and said vessel, said joint com prising a lurality of metallic members oined toget er by means of non-conducting vitric material, such as glass, the vitric material adhering to the metal with which it is in contact, the coefficients of expansion of the adjoining metallic members and vitric material being of approximately the same value, the differences if any in each instance being so small, that excessive contraction or expansion strains due thereto cannot develop.

3. An electrical 'device comprising an evacuated vessel, an electrode element within said vessel, said electrode'element terminating at the exterior of said vessel and an airtight, non-conducting joint supporting said electrode and interposed between said electrode and said vessel, said joint comprising a pile-up consisting of alternate layers of metal discs and non-conducting vitric material, said discs being welded together by said vitric' material, the coefficients of expansion of said metal discs being, ineach instance, approximately the same as the vitric material adhering thereto.

4. The method of producing an airtight electrically insulated joint between two metallic members by means of a vitric material having a coefficient of expansion differing materially from those of the metallic members which consists in securing to each of.

said metallic members a metallic part hav ing a coefficient of expansion substantially equal to that of the vitric material, applying the vitric material to the exposed surface of at least one of said metallic parts, subjecting said vitric material to a softening temperature and pressing said parts together with the softened vitric material inter'posed therebetween, suflicient pressure heing applied to cause the two metallic parts to adhere one to the other.

In testimony whereof I afiix my signature.

EZECHIEL WEINTRAUB. 

